THE US civil rights advocate Rachel Dolezal, who has been accused of falsely claiming she is African-American, said she identifies as black and has been doing so since she was 5 years of age.

Dolezal, in an interview on NBC's "Today" television show, said a major shift in her identity came when she was doing human rights work in Idaho and newspaper stories described her as transracial, biracial and black.

"I never corrected that," she said, "... because it's more complex than being true or false in that particular instance."

She has also called into question her parentage, saying she has no proof that her white mother and father are her biological parents.

She hadn't had a DNA test to show that Larry and Ruthanne Dolezal, who say their daughter has no African heritage at all, are her birth parents.

"Up to this point, I know who raised me," she said.

"I haven't had a DNA test. There's been no biological proof that Larry and Ruthanne are my biological parents."

Ms Dolezal also called into question the authenticity of her birth certificate, which names Larry and Ruthanne as her mother and father.

"I'm not necessarily saying that I can prove they're not," she said.

"But I don't know that I can actually prove they are. I mean, the birth certificate is issued a month and a half after I'm born. And certainly there were no medical witnesses to my birth."

Dolezal, 37, who grew up with adopted black siblings, resigned on Monday as president of the Spokane chapter of the National Association for the Advancement of Colored People, a leading U.S. civil rights organization.

Her own concept of her race began when she was 5 years old, Dolezal said.

"I was drawing self-portraits with the brown crayon instead of the peach crayon and the black curly hair," she said.

Shown a photograph of herself as a teenager with fair complexion and blond hair in the TV interview, Dolezal said, "I would say that visibly she would be identified as white by people who see her."

Dolezal took issue with critics who have said that by presenting herself as African-American, she was putting on a black-face performance - an outdated act in which white actors used makeup to portray black stereotypes.

"I have a huge issue with black-face," she said. "This is not some freak ... mockery black-face performance. This is on a very real, connected level. I've actually had to go there with the experience."

Dolezal had represented Albert Wilkinson, a black man she worked with in Idaho, as her father and she said they had a family-level connection, according to media reports.

"Albert Wilkinson is my dad," Dolezal said. "Any man can be a father. Not every man can be a dad."

Dolezal said her two sons, who are black, had been supportive of her identity.